(a) Field of the Invention
The present invention relates to a thermoplastic, liquid-crystalline, wholly aromatic polyimide ester and a method of producing the same. Particularly, the present invention relates to a novel thermoplastic, liquid crystalline, wholly aromatic polyimide ester and a method of producing the same, which polyimide ester can be suitably used as engineering plastics for electric and electronic parts, automobile parts, etc. which require excellent dimensional stability and accuracy in both flow direction (machine direction: MD) and a direction making a right angle with the flow direction (transverse direction: TD), particularly in the field of precision injection-molded articles, or in the fields of film, sheet, textile industries or the like.
(b) Description of the Related Art
In recent years, thermoplastic resins having extremely small coefficients of linear expansion in MD have come to be known. These resins are a series of resins called thermotropic liquid-crystalline polymers, and some examples of such resins include the wholly aromatic polyesters disclosed in Japanese Patent Application Kokoku Koho (Publication) No. 63-3888, Japanese Patent Application Kokoku Koho (Publication) No. 58-40976, Japanese Patent Application Kohyo Koho No. 61-501207, Japanese Patent Application Kokai Koho (Laid-open) No. 58-29819, Japanese Patent Application Kokai Koho (Laid-open) No. 58-45224, Japanese Patent Application Kokai Koho (Laid-open) No. 59-30821, Japanese Patent Application Kokai Koho (Laid-open) No. 59-78232, Japanese Patent Application Kokai Koho (Laid-open) No. 64-26631, and Japanese Patent Application Kokai Koho (Laid-open) No. 64-40520.
The above-mentioned polyesters have small coefficients of linear expansion in MD but have much the same coefficients of linear expansion in TD as those of common thermoplastic resins, and are therefore hardly sufficient in dimensional stability.
Improvement of the dynamic properties in TD has been attempted, as disclosed in Japanese Patent Application Kokai Koho (Laid-open) No. 63-146959, generally by introducing into the polyesters inorganic fillers (such as glass fibers, calcium carbonate, etc.). However, no satisfactory results have been obtained from such an attempt.
Polyimide esters containing both imide bonds and ester bonds in their molecules have also been well known. For example, those exhibiting high heat resistance are disclosed in U.S. Pat. No. 3,542,731, those improved in heat resistance, mechanical properties, and processability in Japanese Patent Application Kokai Koho (Laid-open) No. 58-67725, those having high elastic moduluses in Japanese Patent Application Kokai Koho (Laid-open) No. 55-84326, those having toughness in Japanese Patent Application Kokai Koho (Laid-open) No. 58-113222, and those having high rigidity in Japanese Patent Application Kokai Koho (Laid-open) No. 60-4531. However, these polyimide esters are also hardly sufficient in the dimensional stability.